This invention relates to a cam shaft used e.g. for driving intake valves and exhaust valves of an internal combustion engine and a process for manufacturing the same.
As a prior art cam shaft of this type, there is known one disclosed in Japanese Unexamined Utility Model Publication 57-16090.
This prior art cam shaft comprises a shaft member made of a ferrous material and cams made of a sintered alloy or a ceramic material. The cams are fitted on the shaft member and fixed thereto.
In this prior art, the cams are fixed to the shaft by integrally forming gears on the shaft member and at the same time by pouring a synthetic resin between the shaft and the cams.
The above-described prior art requires a mold or a forming machine for synthetic resin to integrally form a gear of synthetic resin on the outer periphery of the shaft member.
To increase the bonding force between the resin and the shaft member, it is necessary to form a resin layer over a substantially entire length of the shaft member. As a result, the diameter of the shaft member has to be reduced.
This reduces the rigidity of the shaft member. Thus if the cam shaft is small in size, problems concerning strength will arise.